全文获取类型
收费全文 | 637篇 |
免费 | 32篇 |
国内免费 | 93篇 |
专业分类
电工技术 | 5篇 |
综合类 | 18篇 |
化学工业 | 98篇 |
金属工艺 | 99篇 |
机械仪表 | 8篇 |
建筑科学 | 1篇 |
矿业工程 | 15篇 |
能源动力 | 74篇 |
轻工业 | 1篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 158篇 |
一般工业技术 | 166篇 |
冶金工业 | 42篇 |
原子能技术 | 38篇 |
自动化技术 | 31篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 10篇 |
2021年 | 14篇 |
2020年 | 23篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 18篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 71篇 |
2010年 | 29篇 |
2009年 | 59篇 |
2008年 | 31篇 |
2007年 | 50篇 |
2006年 | 39篇 |
2005年 | 30篇 |
2004年 | 31篇 |
2003年 | 42篇 |
2002年 | 22篇 |
2001年 | 24篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有762条查询结果,搜索用时 62 毫秒
21.
1 INTRODUCTIONGallium nitride (GaN) is one of the most po tential semiconductors. GaN has a direct energyband gap of 3.4 eV at room temperature and highexternal photoluminescence quantum efficiency, aswell as a high excitonic binding energy of20 meV[1]. It is an ideal material for fabrication ofultraviolet(UV)/blue/green light emitting diodes(LEDs), laser diodes(LDs), UV detectors and de vices operating in high temperature, high frequen cy and high power co… 相似文献
22.
We report current-induced magnetization reversal in a ferromagnetic semiconductor-based magnetic tunnel junction (Ga,Mn)As/AlAs/(Ga,Mn)As prepared by molecular beam epitaxy on a p-GaAs(001) substrate. A change in magneto-resistance that is asymmetric with respect to the current direction is found with the excitation current of 106 A/cm2. Contributions of both unpolarized and spin-polarized components are examined, and we conclude that the partial magnetization reversal occurs in the (Ga,Mn)As layer having smaller magnetization with the spin-polarized tunneling current of 105 A/cm2. 相似文献
23.
研究了镓-邻氯苯基萤光酮-TritonX-100析相显色体系,建立了测定镓的析相光度法。在pH7.0磷酸二氢钾-磷酸氢二钠缓冲介质中,镓-邻氯苯基萤光酮-TritonX-100胶束溶液在95℃加热1h,配合物即被TritonX-100相完全富集.最大吸收峰为575nm,表观摩尔吸光系数为1.05×105L·moL-1·cm-1,镓含量0~8μg/5mL服从比耳定律,采用P350萃取树脂分离,应用于矿石中微量镓测定,结果满意。 相似文献
24.
从烟化炉渣中回收镓的研究概况 总被引:6,自引:0,他引:6
韶关冶炼厂每年产鼓风(烟化)炉水淬渣15万t,其中含Ga30—40t,铁4万t左右,且历年堆放水淬渣近200万t,含Ga达400~500t,以现价计,高达十数亿人民币。韶冶开发部及其它科研院所的科研工作者对韶冶镓回收做了大量的工作。主要以以下四种方法为主:高温氯化挥发法、全湿法流程回收镓、碱熔-浸出法、还原熔炼-电解法等。其中以还原熔炼-电解法的各项指标较为理想,并通过工业试验证明该方案是可行的。 相似文献
25.
《Calphad》2014
Using MHTC 96 Setaram high temperature drop calorimeter, partial and integral enthalpies of mixing of liquid alloys were determined in the Ag–Ga, Cu–Ga and in the ternary Ag–Cu–Ga system. The ternary alloys were investigated along two cross-sections at two different temperatures: 1128 K and 1273 K, respectively. Experimental data were used to find ternary interaction parameters by applying the Redlich–Kister–Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. The experimental data indicate that the heat of mixing in this system is slightly temperature dependent, at least in the measured temperature range. 相似文献
26.
Shun Xu Xuping Lin Ben Ge Desheng Ai Jingtao Ma Zhijian Peng 《International Journal of Applied Ceramic Technology》2019,16(1):108-118
(100-x) wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - x wt.% Ce0.8Gd0.2O1.9 (x = 0, 5, 10, 20) electrolytes were prepared by solid-state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La0.9Sr0.1 Ga0.8Mg0.2O2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm−1 at 800°C. The cell performances based on La0.9Sr0.1 Ga0.8Mg0.2O2.85-Ce0.8Gd0.2O1.9 electrolytes were measured using Sr2CoMoO6-La0.9Sr0.1 Ga0.8Mg0.2O2.85 as anode and Sr2Co0.9Mn0.1NbO6 -La0.9Sr0.1 Ga0.8Mg0.2O2.85 as cathode, respectively. At 800°C, the measured open-circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 electrolyte reach 192 mW cm−2 and 720 mA cm−2, respectively. 相似文献
27.
《International Journal of Hydrogen Energy》2022,47(98):41640-41647
Two-dimensional (2D) materials have been widely developed due to their attractive properties. Here, by using density functional theory (DFT) calculations, for the first time, we explore potential applications of the novel XIS (X = Al, Ga, In) monolayer 2D materials on photocatalytic water splitting. A series of simulations were carried out to predict and study the structural, elastic, phononic, optical and electronic properties of 2D XIS materials. The results show that GaIS and InIS demonstrate low thermal conductivity. For optical properties, AlIS shows strong light absorption coefficients and refractive index only under ultraviolet (UV) light, while GaIS and InIS show stronger performance under both visible light and UV light with the band edge positions spanned the redox potential of water. The reasonable band positions and bandgaps make them promising photocatalysts for water splitting. This work reveals the potential applications of monolayer 2D XIS in thermal, electronic, and photocatalytic water splitting. 相似文献
28.
~(64)Cu,~(68)Ga,~(86)Y和~(89)Zr具备不同的半衰期和特殊生物体内性质,丰富了PET药物的多样性,为疾病的诊断和治疗提供了新的契机。近年来,金属正电子核素~(64)Cu,~(68)Ga,~(86)Y和~(89)Zr标记的药物在正电子发射计算机断层显像(PET)诊断中的应用越来越多,~(64)Cu在乏氧显像中发挥重要作用,~(68)Ga在靶向神经内分泌(NET)类肿瘤的诊断药物领域发展迅速,~(86)Y,~(89)Zr有望在免疫PET和放射免疫治疗领域发挥作用。本文主要综述金属正电子核素~(64)Cu,~(68)Ga,~(86)Y,~(89)Zr的生产与纯化,溶液配位化学以及应用方面的研究进展。 相似文献
29.
《材料与设计》2015
This study investigated the microstructure, phase transformation and mechanical property of Ni–Mn–Ga particles/Mg composites with a strong interfacial reaction between the particles and the matrix. The strong interfacial reaction was related to the large surface area and energy per unit volume of the flaky shape Ni–Mn–Ga particles that favors the reaction between the particles and matrix. The martensitic transformation behavior was largely weakened due to the interfacial reactions and thus the reduced volume fraction of Ni–Mn–Ga particles. The composites exhibited a much improved compressive strength and ductility in comparison with that of the Ni–Mn–Ga alloy. The compressive plasticity of the composites was decreased when the Ni–Mn–Ga particle content exceeded 40 wt%. In comparison with the Mg-composites with large size Ni–Mn–Ga particles, the composites with small size particles would have a much stronger interfacial reactions, which was detrimental to the phase transformation and mechanical ductility of the composites. The investigation results in this article could provide a reference for the design and preparation of the particles reinforced metal matrix functional composites. 相似文献
30.
Wolfram Witte Daniel Abou‐Ras Karsten Albe Gottfried H. Bauer Frank Bertram Christian Boit Rudolf Brüggemann Jürgen Christen Jens Dietrich Axel Eicke Dimitrios Hariskos Matthias Maiberg Roland Mainz Max Meessen Mathias Müller Oliver Neumann Thomas Orgis Stefan Paetel Johan Pohl Humberto Rodriguez‐Alvarez Roland Scheer Hans‐Werner Schock Thomas Unold Alfons Weber Michael Powalla 《Progress in Photovoltaics: Research and Applications》2015,23(6):717-733
The gallium gradient in Cu(In,Ga)Se2 (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co‐evaporation processes, plays a key role in the device performance of CIGS thin‐film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X‐ray measurements. In addition, the gallium grading of a CIGS layer grown with an in‐line co‐evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth‐dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co‐evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi‐Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross‐sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper‐vacancy‐mediated indium and gallium diffusion in CuInSe2 and CuGaSe2 were calculated using density functional theory. The migration barrier for the InCu antisite in CuGaSe2 is significantly lower compared with the GaCu antisite in CuInSe2, which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co‐evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献